This invention relates generally to earth well drilling apparatus and and its use. Particularly, it relates to apparatus that is useful for drilling one or more bore holes extending laterally from a lower region of a well into a mineral bearing formation.
It has been recognized that minerals may be recovered from mineral-bearing formations by introducing such agents as steam, hot water, chemical solutions and the like. For example steam has been introduced into petroleum-bearing sands (e.g. tar sands or heavy oil) and other porous formations to effect the release and removal of petroleum not otherwise having sufficient fluidity to permit pumping from the well. Certain of such equipment and methods employ special drilling apparatus for drilling a laterally extending bore from a region of the well at the level of the formation, after which steam or other treating fluid is introduced into the bore. An example of such drilling apparatus is disclosed in U.S. Pat. Nos. 2,258,001 and 1,865,853. Such prior drilling equipment and methods have been subject to certain disadvantages. In instances where drilling the lateral bore has employed a rotated cutting head which is directed laterally against the formation, the torque may be applied to the head through driving means extending from the top of the well, which requires complicated and expensive means to transmit power through a vertically rotated pipe or shaft to the laterally directed drillhead. If an electrical driving motor is located within the well and coupled to the drillhead, it poses problems in applying the necessary electrical energy and the motor may not be readily salvageable before injecting steam or other treatment fluid. Use of laterally directed jet drilling as shwon in U.S. Pat. No. 2,258,001 requires special flexible piping which carries the drillhead and to which hydraulic liquid under pressure is applied. Among other objections, flexible conduits are not self-supporting when projected laterally and thus require additional supporting means such as a surrounding housing as shown in U.S. Pat. No. 2,258,001.
EPA Publication No. 0 100 230 discloses an apparatus and method making use of hydraulic jet drilling with the drillhead being attached to a drilling tube of the solid wall type. The drilling tube initially is carried within piping extending downwardly into the well and has an open upper end. A seal is provided between the drilling tube and the piping, whereby when hydraulic liquid (e.g. water) under pressure is applied to the piping, it is propelled downwardly. Tube bending means is carried at the lower end of the piping adjacent the mineral bearing formation, and forms an arcuate guide way through which the drilling tube is propelled, thereby causing the drilling pipe to be bent and the drilling head projected laterally into the formation.
The EPA Publication No. 0 100 230 also discloses a retractable whipstock consisting of connected assemblies, which when extended from a retracted position within the structure form an arcuate tube bending guideway. The assemblies have a series of rollers or sheaves rotatably carried to form a segment of the arcuate guideway. The form of the guideway is generally that of an arc of a circle extending to one side only of the apparatus. The segments are formed into the arcuate pathway by applying hydraulic forces from the surface to a hydraulic piston assembly.
Jeter U.S. Pat. No. 4,007,797, purportedly discloses, in FIG. 10 an erectable whipstock (conductor) which projects to both sides of the assembly in which it is contained prior to erection. An attempt to use the Jeter erectable conductor would result in a number of major problems.
One problem with the conductor of Jeter is that the guide, being flexible, and being held by a single actuating rod (80), is incapable of resisting moments required to bend a solid tube. A further problem with Jeter is the use of a piston which acts axially with respect to the drill pipe. Therefore, actuating rod 80 must be relatively short and at a sharp angle to the axis resulting in high stress on rod 80 to bend the rigid pipe. Furthermore, arm 80 is illustrated on the left (top) side of the conductor in FIG. 8 in an unerected position and of the bottom side in FIG. 9. Obviously, this is a paper not real, solution to the erection problem.
Another problem with Jeter is that it includes no rollers or sheaves to engage the inner or outer walls of the bent tube to reduce frictional forces which can otherwise either prevent the tube from bending through the whipstock or cause the tube to buckle in the whipstock. Perhaps recognizing this, Jeter suggests column 10, line 44-52 that the pipe be flattened as it moves through the whipstock and is thereafter reformed into a circular shape. Rigid pipe is not likely to be capable of such drastic changes in shape on moving through the whipstock.